The present invention is directed generally to a self propelled scale testing vehicle of a calibrated weight adapted to transport additional calibrated weights for the testing and calibration of high capacity truck scales.
Platform or heavy capacity scales are used to weigh large quantities of bulk materials, such as grain, gravel, rock, concrete, and other raw materials. In addition, government regulations create a demand for the use of platform scales; for example, to determine whether trucks are in compliance with the various load limits placed on highways by the individual states. Platform scales are commonly used with weight loads ranging from a few tons to several tons.
Platform scales over a period of time have a tendency to provide inaccurate measurements. This is partly due to the environment in which the scales are utilized. Dirt and debris has a tendency to build up at various points in the scale mechanism, thereby restricting the action of the mechanism and also causing wear. When this occurs, the scale does not indicate the true weight of the load.
Therefore it is important to periodically calibrate a heavy capacity scale to assure accuracy. In the past, heavy capacity scales have been tested by placing individual weights, normally 500 pound units or 1,000 pound units upon the platform of a scale. Unfortunately, this method requires considerable amount of time and man power to unload the weights, test the scale and reload the weights onto the weight trasporting vehicle. Additionally, the accuracy of the platform scale may vary at different weight loadings. That is, the scale may indicate the correct weight at one point in its range, but exhibit inaccurate readings in another weight range. Therefore, calibration techniques required by state agencies commonly require a heavy capacity scale to be calibrated at different loading corners or sections of the scale.
Self propelled scale testing vehicles have been developed in an effort to provide a calibration device which is somewhat transportable, which is capable of carrying a varying quantity of calibration weights, which uniformly distributes the weight it is carrying, and which is easily movable about a platform scale. However, most of these vehicles are rather bulky and require transportation by a specially made or heavy duty trailer. Furthermore, the weight of the self propelled vehicle itself is not constant thereby causing a weigh inaccuracy. For example, weight cart calibration apparatus comprising a combustion drive engine and/or a hydraulic drive pump will vary in weight due to the changes in fluid volume. Since the gas in the gas tank varies and the hydraulics will have a tendency to leak out of the various valves, the weight of the cart will not remain constant.
Additionally, self propelled testing vehicles provide rather limited maneuverability and a single or limited range of speed. Accordingly, such vehicles are difficult to maneuver at the scale sight.
Further, self propelled vehicles do not provide for corner testing or calibration of a scale due to their rather large size.
The present invention solves these and many other problems associated with currently existing self propelled scale testing vehicles.